//
// Created by wze-zero on 2024/7/24 024.
//
#include <iostream>
#include <set>

using namespace std;

int main() {
    char str[100];
    cin.getline(str, sizeof(str));
    set<char> s;
    for (int i = 0; str[i] != '\0'; ++i) {
        s.insert(str[i]);
    }
    for (set<char>::iterator i = s.begin(); i != s.end(); ++i) {
        cout << *i;
    }
    cout << endl;
    return 0;
}